Raising water level instead of lowering to close!

I'm getting ready to close our 21x43 foot AG pool. I am not going to cover it. Last year I left a leave net on till all the leaves fell but we got very cold early and the net froze and stayed on most of the winter. This year, no leaf net. No cover at all. I hear everyone say they lower the water level below the skimmer and return. Last year I actually raised my level above both and plugged them. Didn't seem to be any problems. My question is what is the reasoning for lowering the water level for the winter? Or what would be the harm of not?

Ice damage. If you don't have something to keep the ice from filling your skimmer it will break it.